Not Applicable.
Not Applicable.
The present invention relates generally to catheter systems, and more particularly, to catheter systems for ablating and/or isolating foci that contribute to cardiac arrhythmia.
Catheters are commonly used in surgical procedures to access certain areas of a patient""s body without resorting to invasive surgical procedures. For example, catheters are widely used in the field of cardiology to conduct electrophysiological studies in which electrical potentials within the heart are mapped to determine the cause and location of arrhythmia. In many cases, certain undesired conductive pathways, known as foci, contribute to and cause the arrhythmia. Once the location of foci is identified, elements on or within the catheter can be utilized to ablate or isolate the foci, thus eliminating the arrhythmia.
One form of arrhythmia is atrial fibrillation, which is an uncoordinated contraction of the heart muscle within the atrium. Atrial fibrillation results from rapidly discharging foci and causes irregular heart beats, possibly leading to inefficient pumping of blood. In a significant number of patients, the foci that contribute to this condition are located within the pulmonary vein, adjacent to the atrium. These foci may be in the form of scattered groups of rapidly discharging cells. Treatment of this condition can sometimes be effective through the ablation of these foci. However, identifying the location of these foci and effecting the ablative treatment of the foci can be time consuming and difficult.
A variety of cardiac mapping and ablation catheter systems are well known in the art. For example, U.S. Pat. No. 5,476,495 (Kordis et al.) discloses a steerable catheter system that is able to conduct cardiac mapping and ablation. U.S. Pat. No. 5,507,743 (Edwards et al.) discloses a radio frequency (RF) treatment apparatus that includes a RF electrode that assumes a helical orientation upon deployment. U.S. Pat. No. 5,738,683 (Osypka) discloses a cardiac mapping/ablation catheter that includes an electrode that may be deployed in the shape of a loop. U.S. Pat. No. 5,782,879 (Imran) discloses an endocardial mapping and ablation system in which the catheter includes a deployable distal extremity, in the form of a cage-like member that includes a plurality of electrodes.
Despite the existence of these references and existing ablation catheter systems, there exists a need to provide a system that is able to effectively treat atrial fibrillation conditions that are caused by foci present within the pulmonary vein.
The present invention provides a cardiac catheter system for ablating tissue to electrically isolate certain tissue from arrhythmia-inducing foci. Although the invention is primarily shown and described as a cardiac catheter system for ablating tissue with RF energy, it is understood that the system has other applications and embodiments as well. For example, other types of energy, such as microwave, laser, cryogenic, and ultrasonic energy, can be used without departing from the scope of the invention.
In one embodiment, a cardiac ablation catheter system includes an elongate, flexible sheath having an internal lumen and an open distal end. An ablating element is disposed within the sheath and is selectively deployable therefrom so as to project from the sheath in a substantially coil-like shape. In an exemplary embodiment, the deployed ablating element has a geometry forming at least one revolution for generating a circumferential lesion within a vessel, such as a pulmonary vein. In general, the ablating element is oriented in a plane that is substantially orthogonal to the longitudinal axis of the sheath in the deployed position to facilitate the formation of a lesion about the vein inner wall circumference.
The catheter system can include a variety of mechanisms for deploying the ablation member from the catheter. In one embodiment, the ablation member is released from a distal end of the catheter such that it assumes a predetermined shape. In another embodiment, the catheter includes a hatch or port from which the ablation member is selectively deployed. In a further embodiment, the elongate member includes a distal end affixed to a support member that is extendable from the catheter distal end. By rotating and/or longitudinally displacing the support member, the ablation member can be deployed such it assumes a desired size.
To ablate or isolate the target foci tissue, the catheter is manipulated through the arterial network until the catheter is located proximate the desired treatment site. For example, the treatment site may be a location within the pulmonary vein or left atrium at or near the pulmonary vein os or in the right ventricular outflow tract, such as at the junction of the right atrium and superior vena cava. The ablating element is then deployed from the catheter such that the coil-like ablating element is generally oriented in a plane orthogonal to the longitudinal axis of the sheath. The deployed ablating element should be in contact with tissue about the circumference of the vein inner wall, such as at the os. The ablation element is then energized to ablate the target tissue to electrically isolate the foci from healthy tissue on the opposite side of the formed lesion. The atria, for example, can be electrically isolated from a treated pulmonary vein by creating a circumferential lesion on the inner wall of the left atrium or in the pulmonary vein proximate the os.